Concrete is a mixture of aggregates firmly bound into a monolithic mass by a cementing agent. Typically, it is a mixture of a coarse aggregate such as small stones, a fine aggregate such as sand, and a cementing agent such as Portland cement. Concrete is typically formed by mixing the components in fresh water and then permitting the mixture to cure. In this process the voids between the particles of coarse aggregate are filled by the fine aggregate, and the whole is cemented together into a generally impermeable mass by the binding action of the cement. The strength of the cementing agent is a function of the water/cement ratio.
Both sand and fresh water have been historically regarded as necessary ingredients in concrete. Both ingredients are typically specified as substantially salt-free to avoid salt deterioration.
Conventional concrete, however, is wasteful of resources. The cost of suitable sand is no longer negligible, and it is expensive and energy consuming to truck and mix. Similarly, the supply of fresh water is no longer limitless; and, in many parts of the world water is a scarce resource. Conventional concrete, using large quantities of both sand and water, is needlessly expensive and heavy for many applications. Accordingly, there is a need for a cementitious material which can be made without the necessity of sand and fresh water.